PROGRAMMABLE CLOCK GENERATOR 20 NOVEMBER 11, 2016
5P49V5944 DATASHEET
5P49V5944 Application Schematic
The following figure shows an example of 5P49V5944 application schematic. Input and output terminations shown are intended as examples
only and may not represent the exact user configuration. In this example, the device is operated at V
DDD,
V
DDA
= 3.3V. The decoupling
capacitors should be located as close as possible to the power pin. A 12pF parallel resonant 8MHz to 40MHz crystal is used in this example.
Different crystal frequencies may be used. The C1 = C2 = 5pF are recommended for frequency accuracy. If different crystal types are used,
please consult IDT for recommendations. For different board layout, the C1 and C2 may be slightly adjusted for optimizing frequency accuracy.
As with any high speed analog circuitry, the power supply pins are vulnerable to random noise. To achieve optimum jitter performance, power
supply isolation is required. 5P49V5944 provides separate power supplies to isolate any high switching noise from coupling into the internal
PLL.
In order to achieve the best possible filtering, it is recommended that the placement of the filter components be on the device side of the PCB
as close to the power pins as possible. If space is limited, the 0.1uf capacitor in each power pin filter should be placed on the device side. The
other components can be on the opposite side of the PCB.
Power supply filter recommendations are a general guideline to be used for reducing external noise from coupling into the devices. The filter
performance is designed for a wide range of noise frequencies. This low-pass filter starts to attenuate noise at approximately 10 kHz. If a
specific frequency noise component is known, such as switching power supply frequencies, it is recommended that component values be
adjusted and if required, additional filtering be added. Additionally, good general design practices for power plane voltage stability suggests
adding bulk capacitance in the local area of all devices.
The schematic example focuses on functional connections and is not configuration specific. Refer to the pin description and functional tables
in the datasheet to ensure the logic control inputs are properly set.
